On a hot, sunny day, the temperature on the surface of a traditional black roof can be more than 50 degrees Fahrenheit (10 degrees Celsius) warmer than the surrounding air temperature [source: Department of Energy ]. When you imagine that sweltering rooftop next to another, and another, and another, it's no surprise that the air in a large city with block after block of dark, heat absorbing rooftops can often be 6 to 8 Fahrenheit degrees hotter than surrounding areas [source: Heat Island Group].

Even in rural and suburban neighborhoods, the heat absorbed by a traditional roof on a sunny day raises temperatures inside the house, contributing to higher air conditioning requirements, higher energy costs, and more discomfort on hot days for anyone without air conditioning. Fortunately, the remedy for all this extra heat is relatively low-tech, low-cost, and increasingly easy to find: it's called a cool roof.

A cool roof is a roof designed to maintain a lower surface temperature in bright sunshine than a traditional roof [source: Department of Energy]. The surface of a cool roof reflects more sunlight and releases more heat than a so-called hot or dark roof. While the term "cool roof" is sometimes used to describe any roofing surface that is cooler than a standard rooftop, green certification programs such as LEED, Energy Star, the U.S. Green Building Council, and the Department of Energy Building Technology Program base their respective cool-roof credentials on a roofing material's ability to reflect the sun (solar reflectance) and release absorbed heat (emissivity). The higher the solar reflectance and emissivity (on a scale from 0 to 1), the cooler the roof.

Ready to save money, conserve energy, and cool the planet by turning your old, hot roof into a cool roof? Read on to discover 10 ways to cool your roof!